1. Statement of the Technical Field
The invention concerns filtration equipment. More particularly, the invention concerns a method for filtering contaminant and/or sediment particles from a fluid being pumped (or passed) through a filtration material. The filtration medium is formed of layers of mesh material with passages greater in size than the particles.
2. Description of the Related Art
A filter typically consists of a cartridge or bag for use in a pressurized filter system. A pressurized filter system utilizing filter bags is typically comprised of a filter housing having a body and a cover. The body contains a filter basket for placing the filter bag therein. The filter housing is comprised of a mounting stand, an input orifice and an output orifice. A contaminated fluid is pumped into the filter housing through the input orifice. The contaminated fluid is filtered as it flows through the filter bag and then exists through the output orifice. Such a pressurized filter system is disclosed in U.S. Pat. No. 5,246,581.
As should be understood, a filter bag is typically composed of a pre-filtration layer, a filtration layer and a post-filtration layer. Each layer is co-extensive with the surface area of the filter bag. The pre-filtration layer is the inside layer, and thus would be the inside of the filter bag. The pre-filtration layer is often referred to as the upstream layer. The pre-filtration layer is formed of a single layer of a pre-filter material, such as a mesh material. The pre-filtration layer acts as a strainer, i.e., collects large particles from a fluid being pumped through the filter bag.
The post-filtration layer is the outside layer, and thus would be the outside of the filter bag. The post-filtration layer is often referred to as the downstream layer. The post-filtration layer is often formed of a fibrous fabric, such as a non-woven spunbond material. The post-filtration layer is typically joined to the other two (2) layers utilizing any technique known in the art, such as an ultrasonic welding technique. The post-filtration layer is configured to provide structural support to the pre-filtration and filtration layer so that they will not fail (i.e., deform, ripe, teal or break) during a filtration process.
Despite the advantages of such a filter bag, it suffers from certain drawbacks. For example, if a fluid including a large amount of sediment is pumped (or passed) through the filter bag, then the pre-filtration layer experiences premature blinding (or caking). The term “blinding” as used herein refers to the clogging of a filtration medium when pores (or passages) become sealed off due to a buildup of sediment particles during a filtration process. The blinding (or caking) results in an obstruction to the flow of the fluid being pumped (or passed) through the filter bag. The premature blinding provides a filter bag with a relatively short life span. Moreover, the mesh material has inconsistent and undefined pore (or passage) sizes. As such, the pre-filtration layer has only an approximate (or nominal) pore size rating. In effect, the pre-filtration layer is inefficient in collecting particles of a particular size.
In view of the forgoing, there remains a need for an improved method of filtering a fluid including a large amount of sediment. This method needs to eliminate or prevent premature blinding (or caking) of the pre-filtration material. There also remains a need for a filter bag or cartridge design which increases the efficiency of the filter material. A filter bag or cartridge design is further needed which optimally enhances fluid flow while providing an extended life span.